Biogenic Ag Nanoparticles from Neem Extract: Their Structural Evaluation and Antimicrobial Effects against Pseudomonas nitroreducens and Aspergillus unguis (NII 08123)

Abstract

Silver nanocrystals have been successfully fabricated by the bioreduction route using the ethanolic extract of Azadirachta indica (neem) leaves as the reducing and capping agent without solvent interference. The silver nanocrystals were grown in a single-step method, without the influence of external energy or surfactants, and at room temperature. The nanoparticles were prepared from different ratios of silver ions to reducing agent molecules and were characterized by UV–vis spectroscopy and transmission electron microscopy (TEM). The nanoparticles were roughly spherical and polydispersed with diameters of less than 40 nm, as determined with high-resolution transmission electron microscopy (HRTEM). Fast Fourier transform (FFT) analysis and X-ray diffraction (XRD) analysis elucidated the crystalline nature of the nanoparticles. The presence of participating functional groups was determined with Fourier transform infrared (FTIR) spectroscopy. The synthesized silver nanoparticles were analyzed as a potential surface-enhanced Raman spectroscopy (SERS) substrate by incorporating rhodamine B as the Raman reporter molecule. The bioreduction process was monitored through SERS fingerprint, which was evaluated by the change in vibrational energies of metal–ligand bonds. It was possible to detect the SERS spectral pattern of the probe molecules on the Ag nanoparticles without the use of any aggregating agent. Thus, the formation of probable intra- and interparticle hot spots was attributed to evaporation-induced aggregation. Furthermore, stirring and precursor salt concentration influenced the kinetics involved in the fabrication process. The thermal stability of the lyophilized nanoparticles prepared from 0.1 M AgNO3 was evaluated with thermogravimetric analysis (TGA) and had a residual mass of 60% at 600 °C. X-ray photoelectron spectroscopy (XPS) studies were used to validate the compositional and chemical-state information. The biomass-capped silver nanoparticles provided antimicrobial activity by inhibiting the growth of Pseudomonas nitroreducens, a biofilm-forming bacterium, and the fungus, Aspergillus unguis (NII 08123).

One-pot phytosynthesis of nano-silver from Mentha longifolia L.: their characterization and evaluation of photodynamic potential

“…It confirms that the increasing incubation period affects the morphological attributes of AgNP. A narrow and symmetrical peak showed that the nanoparticles are monodisperse and spherical [13]. Our results are in favor of some previously published reports [7,27,28].…”

“…Aqueous extract of the branches was prepared by taking a 1 to 10 ratio of plant material and distilled water respectively and heated on a hot plate at 45°C-65°C for 10-20 min. After the boiling, the aqueous extract was filtered under vacuum by using celite and used immediately as fresh for the reduction of silver salt into AgNPs [13].…”

“…Functional groups provide the surface modifications and functionalities to phyto-fabricated nanoparticles and help them to selectively treat pathogens. Previous studies explain that the carboxylic, amine and hydroxyl groups of secondary metabolites play an important role in the reduction process [13].…”

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“…Higher the concentration of the AgNPs higher the SPR band and vice versa. 12 It was confirmed that the temperature is not only the factor to design the nanoparticles but the concentration of the metallic salt also contributes toward the synthesis along with the incubation period. It was also observed that the SPR band was shifted gradually toward the longer wavelength with an increase in the incubation period (Redshift).…”

“…10,11 Cancer is reported as a leading cause of death with around more than 10 million cases every year and is caused by clonally selected mutations in key tumorsuppressor genes and oncogenes. 12 Conventional treatment of cancer involves the surgical removal of cancer sites, chemotherapeutic and radioactive killing of the cancer cells but these treatments often lead to the deterioration of the patient's body and development of resistance in cancer cells against treatment that negatively affect the treatment success rate. [13][14][15] Colorectal cancer is the third most common cancer and makes 10% of all reported cases worldwide.…”